Field of the Invention
The present invention relates to a metal gasket according to a sealing technology. The metal gasket according to the present invention is used, for example, in an automotive field or the other fields.
Description of the Conventional Art
In a tabular metal gasket, a seal bead has been conventionally formed on a flat surface thereof, and the tabular metal gasket has sealed internal pressure and water from an outer side by compressing the seal bead when being fastened by bolts. As well as a seal portion is brought into line contact by forming the seal bead, thereby increasing a sealing surface pressure, the seal bead is required for making the seal portion follow to the flatness of the other surface.
In recent years, it has been essential to downsize and weight save a flange in an engine, an auxiliary machine, and an inverter for an electric vehicle and a hybrid electric vehicle, for improving a fuel consumption of a vehicle such as a motor vehicle. In connection with this, the flange has been reduced its thickness, and the flange has been lowered its rigidity. As a result, even in a field of the metal gasket which is installed to the flange, there has been demanded provision of a gasket which can correspond to the low rigidity.
However, since the flange has the low rigidity, there is a case that the flange in the other side deforms when being fastened by the bolts (the flange is deformed even if the gasket is not assembled), an amount of compression of the seal bead comes short, and a sealing performance can not be obtained.
Further, in addition to the above, there is a case that the amount of compression or the seal bead comes short and the sealing performance can not be obtained since an amount of deformation of the flange becomes greater as a distance between the bolts (a distance between the fastening bolts) becomes longer.
On the other hand, there are inventions described in Japanese Unexamined Patent Publication No. 62-155375, Japanese Unexamined Patent Publication No. 59-188351 and Japanese Unexamined Patent Publication No. 8-93918 as the prior arts relating to the sealing performance between the fastening member such as the bolts and the metal gasket.
Further, there is a demand of addressing narrowness of the seal surface in addition to the above, and there is a case that a space applying the seal bead does not exist in the vicinity of the bolt hole.
However, none of the inventions described in the above patent documents 1 to 3 can meet the demand of addressing the narrowness of the seal surface.
More specifically, in the invention described in the patent document 1, since bolt holes 51 and a seal bead 52 are arranged at different positions on a plane as shown in FIG. 10, the invention can not respond to a request for narrowing a width of a seal surface.
In the invention described in the patent document 2, a magnitude (a diameter d) of a bolt hole 51 is set to be approximately fixed regardless of a specification of a gasket as shown in FIG. 11. However, since a relationship of a maximum width W1 of a seal bead 52 in relation to the magnitude (the diameter d) of the bolt hole 51 is set to d<W1, the invention can not respond to the request for narrowing the width of the seal surface.
In the invention described in the patent document 3, a magnitude (a diameter d) of a bolt hole 51 is set to be approximately fixed regardless of a specification of a gasket in the same manner as shown in FIG. 12. However, since a relationship of a maximum width W1 of a seal bead 52 in relation to the magnitude (the diameter d) of the bolt hole 51 is set to d<W1, the invention can not respond to the request for narrowing the width of the seal surface.